Feeder



y 22, 1952 E. MARTIN 2,604,216

I FEEDER Filed Feb. 14, 1948 5 Sheets-Sheet l W i i INVENTOR EUGENE MARTIN Y 1952 E. MARTIN 2,604,236

FEEDER Filed Feb. 14, 1948 3 Sheets-Sheet 2 EUGENE MARTIN Attorney July 22, 1952 E. MARTBN FEEDER 5 sheets -shet 5 Filed Feb. 14, 1948 Patented July 22, 1952 UNI-TED STATES PATENT OFFICE FEEDER Eugene Martin, Wesleyville, 2a., assignor to Read Standard Corporation, a-corporation offDjelaware Application February 14, 1948, Serial-NmS-Afil r (Cl.j21'i-''17),

,12 Claims.

' This I invention relates j, to; material feedin means;v and particularlywto a reciprocating -piston itype f ceding mechanism for delivering: material ato a receiver: from .a: source: of supply, in which a pressure :difierential exists. between the receiverv andi'the source of supply. While the invention -.is zsusceptible.:t.to (many applications,v it

issparticularly adaptedzfonfeeding finely divided coal from a feed :hopper atatmospheric pressure into ia.;-.coal.receivingrtank in which .thepressure 1' may main-excess of 150 .pounds per 7 squaresinch.

Itxis an object of ;the :invention to provide an improved feed; mechanism of thecharacter described wherein friction incident to reciprocation ofiither -feedipiston in .the-:cylinder is minimized, while maintainingoatall'ztimes an 1 effectual iseal against escape ofnpressure: past the .piston from i the pressurized outlet to the: non-pressurized .inlet,:and. generally to provide aapra-ctical andwefficient feedingsapparatus.

1 Another object is to provideaiconstruction and I arrangement :of parts, whereby the operation of I devices of the above character is improved; with I respect to obtaining high feedingcapacity while maintaining the 1 overall idimensions at .a minil'l'llllli'.

Another object is to provide afe'ed mechanism of the character described in which material is delivered from a non-pressurized source of supply to a pressurized receiver on both the forward and return stroke of thefeed piston.

Another object is toprovide improved feed mechanism of the character described including novel means'for completely discharging material from'the feed'piston into the pressurized receiver,

the operation of the said discharging means being synchronized with the operation of the pistonto function when the material carryingcavities-of 'th'episton communieatewith the pressurized outlet.

Additional objects;- advantages and features of 'the'invention reside in the construction, arrangement-and-combination of parts, aswill' be understood from the -preferred and'practical embodiment ofthe invention hereinafter described and, illustrated in the accompanying drawings; in

which Figurezlis a-view .in side elevation of the'novel feedmechanism' with thezfeed hopper and re- 'ceivingtank' to which it is applied also shown in: elevation and partly broken away;

, Figure 2 :is ailongitudinal vertical central section :throughcthe. .novel feed mechanism;

'Figuri3 is: a: sectional view takenzonntheyline 3+4 ofiFigurez; :1-

Figure A isaflsectionallview taken. on. the line 4 l'.of I-FigurehZ;

Figure 5 isiarplan view ofithe novel feedmech'aanism with al-portionbroken, away andshown in horizontal central section Figure -.6is .a sectional view. taken on theeline Figure '7 ansectional .view takenronsthe line 11-71 of Figure 5.

While theieed mechanism =constituting-myin- 'vention maybe. employed for feeding. of various kinds of granular or finely divided. solid .material -from a; source ,of supply to. a .point or dis.-

Charge, it is particularly adapted for delivery .oiwfinely divided coalinto a;pressurized ,receiver,

and it will be sodescribed hereinafter.

The feeding device I Ilecomprises: a cylinder I 1, preferably formed for or reasons a later explained, by end-toz endrelated cylindrical housingtsections I 2.1. I 3.,and -I 4, asbest shown, in: Figured. 'I'heintermediatehousing section. I 31s providedbetween its ends with a downwardly opening. discharge spout -I iconnected with aspressurized tank orrreceptacle IB-..into. which coal drops .by gravity from the feedingdevice I0.

The other housing sections, I2 and I 4 are provided respectively, at their-ends adjacent thereintermediate .orddischarge .housing section. v. I 3' with upwardly; opening. intake. spouts. I1 I and IBi-arranged toreceive coal bygravity from .thethopper I9. Thegintake and dischargespoutsare thusfoilset, or spacedragdistance apart longitudinally of ;the feeding; device,, with the discharge spout v I 5-being between andequidistantrrom the intake-spouts I I and I8. l

Theghousing sectionsul 2', I 3 and H are vrigidly secured, together in any. suitable manner,, as for example. by Joolts 2 D passing throughthe abutting flanges 2| and "22 of the housingvsectionslzjand I3, .andbolts 23passingthrough' abutting flanges 24 and 25" of the housing sections I3: and I4 As best shown in Figures -2and '5; the end of'the housing-section I2-'-opposite theflange' 2I -is open andcommunicates in-end=to end relation with the crankcase- 1'26; Suitable :means; as bolts 21, rigidly A securethe V crank case 26 te :"the flange 28--of'-the-h0using section I2 'Ihe opposite end of *the -crank-- case 26 is provided with-a: crank 1 case cover 2 9 suitably; secured, as by bolts 30. "-to the'cran-k case26.

A 1 hollow: piston 3 I" is mounted; as hereinafter described; to reciprocate in the, cylinder H 1 and isgprovidedwith-theiongitudinally.spacedpockets 32:; and 133 22 extending vertically 1: therethrough. These: pocketsnare .iarrangedis'or that; ;inaone.1ex-

into the cylinder I I behind the piston 3|.

treme position of the piston 3| the pocket 32 registers with intake spout I1 while the pocket 33 registers with discharge spout I5 as shown in Figure 2, and in the other extreme position of the piston 3|, the pocket 33 registers with intake spout I8 while the pocket 32 registers with discharge spout I5.

The pockets 32 and 33 are identical in form and in describing the pocket 32 it will be understood that this applies also to the pocket 33. The pocket 32 is defined by the opposed transversely extending upright walls 34 and 35 and the opposed longitudinally extending upright walls 36 and 31, which, as best shown in Figures 2 and 6 diverge slightly from their upper to their lower ends, thus facilitating discharge of coal from the pocket when in registering position with the discharge spout I5. The pocket defined by the walls 34, 35, 36 and 31, is rectangular in horizontal section, as clearly shown in Figure 5, with the longitudinally extending walls 36 and 31 being preferably spaced farther apart than the transversely extending walls 34 and 35.

The piston 3| is provided with the cylindrical sleeve extensions 38 and 33, so that when the pocket 33 is moved to registering position with the discharge spout l5, as best shown in Figure 2, the sleeve 39 will close off the bottom of the intake spout I8 preventing the coal from dropping The sleeve 38 performs a similar function when the cavity 32 is moved from the position shown in Figure 2 to registering position with the discharge spout I 5.

As clearly shown in Figure 2, a slight clearance is provided between the periphery of the piston 3| including its sleeve extensions 38 and 39, and the innermost surfaces of the cylinder N, there- 'by minimizing scoring, abrasion and freezing of the piston 3| in the cylinder I by the coal dust and particles that find their way between the piston and cylinder during operation.

The piston 3| is provided at its opposite ends with the longitudinally extending piston rods 40 and 4|. The rod 40 is slidably mounted in a bear- 'ing 42 carried by a sleeve 43 which is preferably 'integrally formed with the upright wall 44 of the crank case 25. Similarly, the rod 4| is slidably mounted in a bearing 45 carried by a sleeve 46 which is preferably integrally formed with the end wall 41 of the cylindrical housing section I4.

are secured in any suitable manner in the side hwalls of the crank case 26.

A pair of connecting rods 53 and 54, one at each side of the piston rod 40, operatively connect the crank 55 of the crank shaft 48 with the piston 3| The connecting rods'53 and 54 are rotatably mounted at one of their respective ends on the crank 55 and are oscillatably mounted at :theirirespective opposite'ends on the respective opposite ends of a transversely extending wrist pin 56carried by the piston 3|. The crank 55 is formed with a throw equal to one-half the horizontal distance between the center line of either intake spouts I1 or I8 and the center line 'of' the'discharge spout I5, 'sothat upon recipro- 'cationof the piston 3|, the pockets 32 and 33 of "the piston 3Iwi1l alternately register with the 4 intake spouts I1 and I8, and the discharge spout I5.

Since, as previously stated, clearance is provided between the piston 3| and cylinder II, a pressure seal is provided between the non-pressurized intake spouts I1 and I8, and the pressurized discharge spout I5, in order t prevent escape of air from the pressurized discharge spout I5 through the said clearance and the blow back of coal therethrough.

The pressure seal is formed by a plurality of nonmetallic packing rings 51 surrounding the piston 3| and arranged to be received in an annular recess 58 of the inner wall of the housing section I3 of cylinder I I, the recess 58 being disposed between the intake spout l1 and discharge spout I5. Similar packing rings 59 are received in an annular recess 60 of the inner wall of the housing section I3 of cylinder II, the recess 60 being disposed between the intake spout I8 and discharge spout I5. Spacer members 6| and 62 may be employed to suitably space the packing rings 51 and 59. It is also desirable to provide packing rings 63 and 64 between the cylinder II and piston 3| adjacent the sides of the intake spouts I1 and I8, respectively, opposite the packing rings 51 and 59, in order to minimize the leakage of fine particles of coal into the gear casing 26 and the housing section I4.

It is apparent from the above description that the outer surface of the piston 3| is entirely out of bearing contact with the cylinder II, thereby minimizin abrasion and scoring of the piston and preventing seizing or binding of the piston in the cylinder by reason of coal particles that find their way between the cylinder and piston. The construction described, also provides an effective seal between the non-pressurized coal intake spouts and the pressurized coal discharge spout, permitting feeding of coal into the tank I6 in which the pressure may be for example, 150 pounds per square inch, from the bin I9 which may be at atmospheric pressure, with a minimum of escape of pressure and blow back of coal. The differential in pressure between the intake and discharge spouts may be greater or less than 150 pounds, the above example being cited for purpose of illustration only.

The upper and lower ends of the pocket 32 are provided, respectively, with the longitudinally extending spaced ribs 65 and 66 joining the walls 34 and 35 that define the cavity 32. The outer ends of the ribs 65 and 66 are flush with the circumference of the piston 3| and serve to prevent the upper and lower edges of the walls 34 and 35 from catching against the packing rings 51 as the piston 3| reciprocates. The pocket 33 is provided with similar ribs performing a similar function, and are therefore not described further. As best shown in Figure 6, the walls'36 and 31 of the pocket 32 form with the cylindrical wall of the hollow piston 3| longitudinally extending passages and 9| which together with the similar passages at each side of the pocket 33 provide communication through the hollow piston 3| between the opposite'ends of the cylinder I I thereby permitting equalization of pressure during reciprocation of the piston 3|.

In operation, with the piston 3| in the'position shown in Figure 2, coal drops by gravity through the intake spout I1 into the coal receiving pocket 32. The piston 3| is then moved to the right through the crank shaft 48 and connecting rods '53 and 54 from a suitable source of power (not shown), to a position in which thezpocketd zr'registers with iihEEDIBSSLlIiZBd dis; charge spout J 5: Coal drops by: "gravityzfromrthe cavity 32Fthrough theodischarge-" spout I5 :and into thel pressurized containen l 6; At the same. time,- the cavity"33 has moved into register =witlr the intakespoutt- I6; andreceives coal from th'e hopper 9 while the coal in i cavity 32: is being discharged. on the-return stroke of the'piston 3i the cavities 32 and '33" will 'zreassume ethe po-- sitionsrshown in Figure-2, whereuponthe coal in cavity--33 drops through dischargespent and the cavity 32 receives anothencharge of coal from the intake spout I I.

In order to facilitate discharge of coal from thecavities 32 and 33 the-means, nowdescribed; is provide'ds Theupper wall'porti'on of "thethous" in'g: section" I3 opposite-the discharge spout 15 has a -boss 5-! formed therewith" which is provided with. a transversely extending bore 68. A-short pipe section '69-'isthreaded-in one-end or the b'ore 68 and isarranged to communicate" with a'pipe -18 through a valve H; Theipipe l'fl leads from a suitable source of air under pressure which is admitted to -the bore fi8sbyth'e valve H when eitherof the cavities stand 33' registers with the discharge spout l5;

The valve '1 I, which is normally closed, is

-moved-to its open position upon contact of the shoulders 12 and 130i a segment shaped cam M with the valve stemlfi. Thecamld is pivotally mounted on a bracket 16" which also forms a supportfor the valve H, as-best'shown in Figure 4. Any suitable means may' beprovided for securing the bracket T5 to one side ofthe housing section l3.

The cam 74' is oscillated by meansoperatively connectedto the crank shaft 48 for'alternately bringing the cam shoulders l2and H3 in engagement with the valve stem '55; This means includesa crank pin 7'! secured eccentrically on the endof the crank shaft 58;71'1'101'1 is connected by the 'pitman '18 with a stud l9 fixed to the cam 14 between its pivot and its periphery. Through the described connections, rotation of the crank shaft 38 effects oscillation of thecamd l."

With both the'ca'm' l4 andthe piston 3l-operated=frorn the crank shaft 43, their movements are" synchronized so-that when the cavity33-is in discharging relationwith the discharge'spout l5, as shown in the drawings; the cam El-isin a position so that cam shoulder 15' opens" the valve H, whereby air'under pressure entersthe bore 58; A plurality of orifices 80 provide communication'between the bore'68- and the inside ofthehousing section 53, through which orifices jets of' air under pressure are directedinto" the upper end of cavity 33; facilitating discharge'of coal from the cavity 3-3. Preferably, the pressure of-th'e air jets is greater'than the pressure in the receiving tank [6.

Now," when the piston '3! "moves to the-right, thecam l4 swings in a clockwise direction about its pivot, so thatas the cavity 33 ofpiston 3! moves out of register with discharge spout [5, the shoulder 13 of cam 14 becomes disengaged from valve stemlfi} permitting valvell to close and interrupting passage 1 of air under: pressure to'bore'68 and OrificesBB? 1 Asthe piston 3! moves to the end of its stroke, the cavity 32 registers with the discharge spout |5-and the cam-shoulder 12 engages the valve stem "I5, again opening valve?! and admitting air underzpressure to the bore: 68' and orifices-.80;

While the cam and valve? arrangement a has been: described above with reference. to admittingi air iunder l-pressure. :to". a; pair. ofi'coalireceiving piston cavities, when said cavitiesiiale ternately communicate with the pressurized dischargespout, it is apparentithatt the: same? art rangement maybeused wherera single:. cavity.in the piston. alternately communicates withia coal intake opening and: a discharge .sp'out, by providing -merely one cam shoulderriniplace of the two'cam'shoulders'lz and 13 as shown in. Fig! ure'l;

Uponthe coal being discharged from 'thecavi ties" 32- and 33, a pressure is built-up in: the cavities" since they are in communicationzwith the pressurized tank It. In order to prevent re-'- lease of this pressure into'the hopper '19 through the coalintake spouts ll andl I8; which would otherwise interfere with the free flow of 'coal into the-cavities Hand 33, vents 8| and82'are' pro vided in theupper wall ofthe-h'ousihg section I3 between the discharge spout [hand the intake spouts I l and'lB, asbest shown in Figure 2; The vents 8| and fizpreferably communicate with the passages 83 and 84, respectively, which are formed in the housing section l3 and open to atmosphere. If desired the passages 83 and 84 may be connected to a source of suction to facilitate release of pressure from the cavities'32 and" 33.

My prior application Serial No. 752,849, filed June 5, 1947; relates to the same general subject matter; and'the disclosure in that application is intended to be incorporated herein bythis reference in'the interest of brevity; The generlc' claims will be made in the 'present'application:

I claim:

1. Feed mechanism for delivering material froma non-pressurized zone into a pressurized zone, comprising a cylinder'having ofi'set intake and discharge openings communicating respec tively with said non-pressurized'and pressurized zones, a reciprocating piston in said cylinder, said piston beingprovided with'a pocket communicat ing'in' one position of the piston in receiving relation with said intake opening'and in another position of the piston in discharging relation with. said discharge opening, said piston having a passage extending lengthwise therethrough for equalizing the pressure in the opposite ends of said cylinder as said piston reciprocates, and means within'said cylinder between saidopenings and embracing said piston to form a sealbetween saidcylinder and piston against escape ofipres sure from said pressurized zone to said.non.- pressurized zone.

2. Feed mechanism for delivering material from a none-pressurized zone intov a pressurized zone, comprisinga cylinder having offset intake and discharge openings communicating respectively with said non-pressurized and pressurized zones, a reciprocating piston in said cylinder, said piston being. provided with a pocket communicatingain one position of the piston in receivingv relation with said intake opening and-in another position of the piston in discharging relation with said discharge opening-,venting means for releasing pressuretrapped in said pocket prior to recommunication of said pocket with said intake opening, saidpiston having a passage extending lengthwise therethrough for equalizing the pressure in the opposite ends of said cylinder as said piston reciprocates, andmeanswi-thin said cylinder between-said openings and embracing saidpiston to. form a seal between said cylinderv and 7 piston. against escapeof pressure from said pressurized zone to said non-pressurized zone.

3. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having offset intake and discharge openings communicating respectively with said non-pressurized and pressurized zones, a reciprocating piston in said cylinder, bearing means carried by said cylinder for slidably supporting said piston out of surface contact with the inside wall of said cylinder, said piston being provided with a pocket communicating in one position of the piston in receiving relation with said intake opening and in another position of the piston in discharging relation with said discharge opening, and means within said cylinder on each side of said discharge opening embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone. 1

4. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having offset intake and discharge openings communicating respectively with said non-pressurized and pressurized zones, a reciprocating piston in said cylinder, said piston being provided with a pocket communicating in one position of the piston in receiving relation with said intake opening and in another position of the piston in discharging relation with said discharge opening, a plurality of spaced members Within said cylinder between said openings and embracing said piston to form a. seal between said cylinder and piston against escape of pressure from said pressurized zone to said non-pressurized zone, said piston having a passage extending lengthwise therethrough for equalizing the pressure in the opposite ends of said cylinder as said piston reciprocates, and said cylinder being provided between said plurality of spaced sealing members with a vent arranged for communication with said pocket on the retracting stroke of said piston for releasing pressure, trapped in said pocket, prior to recommunication of said pocket with said intake opening. 5. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having offset intake and discharge openings communicating respectively with said non-pressurized and pressurized zones, a reciprocating piston in said cylinder, bearing means carried by said cylinder for slidably supporting said piston in peripheral spaced relation with respect to and out of surface contactwith the inside wall of said cylinder, said piston being provided with a pocket communicating in one position of the piston in receiving relation with said intake opening and in another positicn of the piston in discharging relation with said discharge opening, a plurality of spaced members within said cylinder between said openings and embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone to said non-pressurized zone, and said cylinder being provided between said plurality of spaced sealing members, with a vent arranged for communication with said pocket on the retracting stroke of said piston for releasing pressure, trapped in said pocket, prior to recommunication of said pocket with said intake opening.

6. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having a pair of spaced intake openings adapted for communication with said non-pressurized zone and a discharge opening intermediate said intake openings adapted for communication with said pressurized zone, a reciprocating piston in said cylinder, said piston being provided with a pair of pockets so spaced that they communicate respectively with one of said intake openings and said discharge opening in one position of said piston and with the other of said intake openings and said discharge opening in another position of said piston, said piston having a passage extending lengthwise therethrough for equalizing the pressure in the opposite ends of said cylinder as said piston reciprocates, and means within said cylinder between said discharge opening and each of said intake openings embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone to said non-pressurized zone.

7. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having a pair of spaced intake openings adapted for communication with said non-pressurized zone and a discharge opening intermediate said intake openings adapted for communication with said pressurized zone, a reciprocating piston in said cylinder, bearing means carried by said cylinder for slidably supporting said piston in peripheral spaced relation with respect to and out of surface contact with the inside wall of said cylinder, said piston being provided with a pair of pockets so spaced that they communicate respectively with one of said intake openings and said discharge opening in one position of said piston and with the other of said intake openings and. said discharge opening in another position of said piston, and means within said cylinder between said discharge opening and each of said intake openings embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone to said non-pressurized zone.

8. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having a pair of spaced intake openings adapted for communication with said non-pressurized zone and a discharge opening intermediate said intake openings adapted for communication with said pressurized zone, a reciprocating piston in said cylinder, said piston being provided with a pair of pockets so spaced that they communicate respectively with one of said intake openings and said discharge opening in one position of said piston and with the other of said intake openings and said discharge opening in another position of said piston, bearing means carried by each end of said cylinder for slidably supporting said piston in peripheral spaced relation with respect to and out of frictional contact with the inside wall of said cylinder, venting means for releasing pressure trapped in said pockets prior to recommunication of said pockets with said intake openings, and means Within said cylinder between said discharge opening and each of said intake openings embracing said piston to form a seal between said cylinder and piston against escape of pressure from said p essurized zone to said non-pressurized zone.

9. Feed mechanism for delivering material from a -p ur zed Zone into a pressurized zone, comprising a cylinder having offset intake and discharge openings communicating respectively with said non-pressurized and pressurized zone, a piston in said cylinder, means for reciprocating said piston, said piston being provided with a pocket adapted for alternate communication with said intake and discharge openings, means within said cylinder between said openings and embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone to said nonpressurized zone, a passage adapted to receive pressure fluid from a source of supply and deliver it into said cylinder diametrically opposite said discharge opening, a valve interposed in said passage, and actuating means coordinated with said piston operating means for opening said valve only when said piston pocket is in communication with said discharge opening.

10. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having offset intake and discharge openings communicating respectively with said non-pressurized and pressurized zones, a reciprocating piston in said cylinder, said piston being provided with a pocket adapted for alternate communication with said intake and discharge openings, means within said cylinder between said openings and embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone to said non-pressurized zone, a passage adapted to receive pressure fiuid from a source of supply and deliver it into said cylinder diametrically opposite said discharge opening, a valve interposed in said passage, a pivotally mounted cam for opening and closing said valve, and means for operating said piston and cam in timed relation, said cam being formed to open said valve only when said piston pocket is in communication with said discharge opening.

11. Feed mechanism for delivering material from a non-pressurized zone into a pressurized zone, comprising a cylinder having a pair of spaced intake openings adapted for communication with said non-pressurized zone and a discharge opening intermediate said intake openings adapted for communication with said pressurized zone, a piston in said cylinder, means for reciprocating said piston, said piston being provided with a pair of pockets so spaced that they communicate respectively with one of said intake openings and said discharge opening in one position of said piston and with the other of said intake openings and said discharge opening in another position of said piston, means within said cylinder between said discharge opening and each of said intake openings embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone to said non-pressurized zone, a passage adapted to receive pressure fluid from a source of supply and deliver it into said cylinder diametrically opposite said discharge opening, a valve interposed in said passage, and actuating mean 00- ordinated with said piston operating means for opening said valve only when said piston pockets are in communication with said discharge open- 12. Feed mechanism for delivering material from a non-pressurized zon into a pressurized zone, comprising a cylinder having a pair of spaced intake openings adapted for communication with said non-pressurized zone and a discharge opening intermediate said intake openings adapted for communication with said pressurized zone, a reciprocating piston in said cylinder, said piston being provided with a pair of pockets so spaced that they communicate respectively with one of said intake openings and said discharge opening in one position of said piston and with the other of said intake openings and said discharge opening in another position of said piston, means within said cylinder between said discharge opening and each of said intakeopenings embracing said piston to form a seal between said cylinder and piston against escape of pressure from said pressurized zone to said non-pressurized zone, a passage adapted to receive pressure fluid from a source of supply and deliver it into said cylinder diametrically opposite said discharge opening, a valve interposed in said passage, a pivotally mounted cam for opening and closing said valve, and means for operating said piston and cam in timed relation, said cam being formed to open said valve only when said piston pockets are in communication with said discharge opening.

EUGENE MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 674,685 Payson May 21, 1901 1,230,811 Shippee June 19, 1917 1,396,859 Long Nov. 15, 1921 

